Jig for drilling pistons



Sept. 1, 1936. v H U T 2,052,924

JIG FOR DRILLING PISTONS Filed Aug. 25, 1934 1 INVENTOR WlTNESSESaY I v r 1". flutter,

' a 7 BY 1 @f M IM r Patented Sept. 1, 1936 UNITED STATES PATENT OFFICE 2 Claims.

My invention relates to improvements in jigs for aiding in the drilling of oil holes in pistons in internal combustion engines, and it consists in the combinations, arrangements and constructions herein described and claimed.

Present day high speed motors for internal combustion engines are prone to use too much oil. One reason is that the oil is trapped by the piston rings and eventually finds its way into the combustion chamber where it is consumed.

In order to obviate this condition, the method in ordinary use is to drill holes in the center of the ring groove extending into the interior of the piston, the object being to return trapped oil to the crank case. This is objectionable because it allows a space above and below the edges of the holes to trap and hold the oil and when the piston reverses direction at the top and bottom of the stroke the oil is valved out over the surface of the ring and passes up to the next ring above and so on into the combustion chamber to be consumed. The wiping effect of the ring on the down stroke tends to collect the surplus oil in the cavity back of the ring in the groove, and as the piston reverses direction at the top or bottom of the stroke a large part of the oil is retained in the groove.

An object of my invention is to provide a jig by means of which oil drain holes may be drilled in a piston having piston ring grooves, half of the hole being in registration with the lower ring groove and the other half being below the ring.

A further object of the invention is to provide a novel form of jig by means of which the holes described above may be readily and accurately bored in pistons of existing types.

A further object is to provide a jig of the type which consists of few parts, and which may be firmly secured to the piston or removed therefrom with very little efiort.

Other objects and advantages will appear in the following specification and the novel features of the invention will be particularly pointed out in the appended claims.

My invention is illustrated in the accompanying drawing forming part of this application, in which:

Figure 1 is a side view of a portion of a piston having oil drain holes therein.

Figure 2 is a sectional view along the line 22 looking in the direction of the arrows.

Figure 3 is a vertical sectional view through a portion of the piston and through the jig showing the application of the latter to the piston.

Figure 4 is a perspective view of the jig, and,

Figure 5 is a bottom view in perspective of a. portion of the jig.

In carrying out my invention I may make use of a piston of ordinary type such as that shown at 6 in Fig. 1. This piston is provided with the 5 usual grooves I, 8 and 9 for the piston rings. At I0 I have shown a series of bores constituting drain openings extending through the piston wall 6 into the interior so that the oil may drain on the interior wall into the crank case. These 10 drain openings or passages ID are located so that the lower part of the openings or passages is below the lower wall of the groove 1, while the upper part is above the wall and therefore in registration with the groove. 15

Such a construction obviates the difliculties heretofore mentioned because all of the surplus oil in the groove would be ejected at the bottom of the stroke and the groove would be empty on the up-stroke to repeat the cycle to collect and 20 discharge the oil back into the crank case. No other change in the general build or construction of the piston would be required.

In order to make these oil drain openings or passages in pistons that have been used, as for 5 instance those that are in automobiles brought to garages for repairs, or to make them in pistons which are to replace other pistons, I make use of the jig shown in Figs. 3 to 5. This jig consists preferably of a rectangular block 30 I I, having a lateral extension or flange l2 which is substantially of the same thickness as the width of the groove 1. The block II is provided with screw holes l3 to receive screws I4. A plate l5, of a thickness substantially that of 35 the width of the groove 8 and designed to enter the groove, is provided with openings arranged to freely receive the screws l4 and it is provided with another opening to receive a screw is which is operated by a handle IT. The block II has a guide bore l8 and the upper half of this guide bore is extended through the flange l2, as shown in Fig. 5, the lower half in the block being below the flange, as clearly shown.

In using the jig the flange I2 is inserted in the 45 groove 1 as far as it will go, and the plate [5 is placed in the groove 8, the curved edges of the extension I2 and of the plate I5 being in contact with the bottom of their respective grooves. The handle 11 is now rotated until the end of the screw I6 is in contact with the block II when further tightening will cause the jig to grip the piston securely.

A drill bit corresponding to the size of the guide bore I8 in the jig is now passed through this bore and the drain opening I0 is bored so that half is below the lower wall of the groove 1 and the other half is above it.

The unloosening of the screw I! will permit the shifting of the jig to the next position for boring the hole and the operation may be repeated.

I claim:

1. A jig for drilling oil holes in pistons having ring grooves, said jig comprising a body portion having an extension arranged to enter the lower: most groove, a plate arranged to enter the adjacent groove, screws for loosely connecting the plate and the body portion, a screw carried by portion, said body portion having a guide bore extending therethrough, half of said guide bore being below the lower wall of said lower -groov e and the other half being above the lower wall of said lower groove and extending through said extension.

'2. A jig for boring holes in pistons having pise ton ring grooves comprising a body portion having a flange adapted to enter one of said piston ring grooves and being provided with a guide bore extending through the body portion, half of the bore extending through the flange, said body portion being provided with screw openings, a

plate adapted to enter another of said piston ring I grooves and having openings for freely admitting the shanks of the screws, said screws being arhaving means at one end for advancing it toward the loo'dypo'rtion; V

HUGH T. DU'ITER. 

